This invention relates generally to random access memories and more particularly to static random access memories (SRAMs).
As is known in the art, SRAMs have a wide range of applications. It is desirable to minimize the surface area used to form such an SRAM.
In accordance with one embodiment of the invention, an array of SRAM cells is provided. Each one of the cells has a plurality of electrically interconnected MOS transistors. Each one of the cells has a VDD CONTACT and a VSS CONTACT. One of such CONTACTs is disposed centrally within each one of the cells and the other one of the CONTACTs being common to four contiguous ones of the cells.
In accordance with another embodiment, each one of the cells has the common one of the CONTACTs and the WORDLINE CONTACT disposed at peripheral, corner regions of the cell.
In accordance with another embodiment, a method is provided for forming a transistor in a semiconductor body. The method includes forming a layer of material having a predetermined vertical thickness over a horizontal surface portion of the semiconductor body. Using the layer of material as a mask, a trench is etched into unmasked portions of the semiconductor body. A source, drain, and gate channel region is formed in a portion of the semiconductor body masked by the layer of material.
In accordance with another embodiment, a gate insulator is formed on a sidewall of the trench. Further, a gate conductors is formed in the trench.
In accordance with another embodiment, a method for forming a transistor in a semiconductor body is provided. The method includes forming a layer of material having a predetermined vertical thickness over a horizontal surface portion of the semiconductor body. Using the layer of material as a mask, a trench is into unmasked portions of the semiconductor body. A source, drain, and gate channel region is formed in a vertical relationship in the surface portion of the semiconductor portion of the semiconductor body masked by the layer of material. Gate conductors are formed over opposite sides of the gate channel region.
In accordance with another embodiment, a method is provided for forming a transistor in a semiconductor body. The method includes patterning a covering material along a horizontal surface of the semiconductor body to provide such material with a vertically extending sidewall portion. A layer of material with a predetermined thickness is conformally deposited a over the horizontal surface of the covering material and over the vertically extending sidewall portion of the covering material to provide a vertically extending portion of such layer of material. The layer of material is anisotropically etched to remove the portion of such material deposited over the horizontal surface portion of the covering material while leaving the vertically extending portion of such layer of material. Using the vertically extending portion of the layer of material as a mask, a trench is etched into unmasked portions of the semiconductor body. A source, drain, and gate channel region is formed in a portion of the semiconductor body masked by the vertically extending portion of the layer of material.
In accordance with another embodiment, the transistors, together with additional such transistors, are arranged to form a Synchronous Dynamic Random Access Memory (SRAM) array. The array includes a plurality of SRAM cells arranged in rows and columns, each one of the cells having a WORDLINE connected to a WORDLINE CONTACT. The WORDLINE CONTACT is common to four contiguous one of the cells. One of the cells having a plurality of electrically interconnected MOS transistors arranged to provide an SRAM circuit. Each one of the cells has a VDD CONTACT and a VSS CONTACT. One of such CONTACTs is disposed centrally within each one of the cells and the other one of the CONTACTs being common to four contiguous ones of the cells. Each one of the cells has the common one of the CONTACTs and the WORDLINE CONTACT disposed at peripheral, corner regions of the cell.